The present invention relates generally to a load bearing member, and particularly to an elongated, insulative support member for aerial high voltage transmission lines.
As transmission voltages are increased to ever higher levels, aerial transmission lines must be spaced greater distances from taller transmission line supporting superstructures or towers. This means that the insulators supporting the transmission lines from the towers must be of greater length. Moreover, the dynamic loading on the transmission lines caused by varying weather conditions such as wide variations in temperature, high winds, icing, etc., imposes tremendous physical stresses on the line supporting insulators. Thus, the insulators must be mechanically robust, in addition to being of high dielectric strength, and consequently are quite heavy in weight and difficult to install. In response to these needs, certain types of insulators have been devised using fiberglass rods as the main structural element. Requisite dielectric strength and protection against the elements is provided by elastomeric weathersheds slipped onto these rods in end-to-end relation. The fiberglass rods are designed to withstand the tremendous compressive, tensile, flexure and torsional stresses incident in the dynamic loading imposed on transmission lines. However, the problem remains to join the requisite fittings to the ends of the fiberglass rod which will accommodate physical connections with the transmission line and the tower. The fitting joints with the rod must also withstand the dynamic loading stresses. Experience has shown that these fitting joints are the weak link in the transmission line insulative supporting structure.
It is accordingly an object of the present invention to provide an improved elongated load bearing member of high mechanical strength.
An additional object is to provide a load bearing member of the above character which is formed of electrically insulative material and thus has application in an aerial high voltage transmission line supporting insulator.
Another object is to provide a load bearing member of the above character having improved end fitting joints.
Yet another object of the present invention is to provide a load bearing member of the above character which is efficient in construction, has a high strength-to-weight ratio, and is reliable in service.
Other objects of the invention will in part be obvious and in part appear hereinafter.